The present invention relates to an automatic arrangement for treating shaping tools on repetitive-cycle machines and, more particularly, to a multinozzle block for spraying all sorts of liquid materials, as coolants, temporary protective and lubricative coatings, under constant reproducible conditions, regardless of the nature of these materials, on the surface of the tools for shaping various materials by molding or plastic deformation. Such multinozzle blocks are particularly suitable for spraying liquids containing suspended solids, without the risk of becoming fouled or stopped up, thanks to a builtin rinsing system.
The coating materials may be thermal insulators, providing protection to the tools, as in the case of molds for die casting metals, thermal insulators with lubricating action, in the case of hot-forging stamps or lubricants, and mold-stripping agents in the case of injection or molding presses for materials such as plastics.
These coating operations, which must be executed repetitively as a function of the machine cycles, generally by spraying and vaporization of such materials in the form of an air-liquid emulsion on the tool surfaces, are performed either manually by the machine operator or automatically by an arrangement composed of a multiplicity of nozzles mounted, with an orientation predetermined as a function of the tool to be coated, on a rigid holder fastened to a manipulating device for moving it into place and retracting it from the position for spraying the tool surface, in synchronism with the machine's operating cycle. A constant volume of the coating material must be sprayed in each cycle, in very diverse positions and orientations, but always identical, and depending on the surface relief of the tool, often being rather inaccessible. French Application No. 69/15,841 which has become French Patent No. 2,044,311 describes such an arrangement.
However, the automation of such operations has always presented great difficulties, not only because of the complexity of the tool surfaces, but also on account of the very nature of the coating material, principally in the die casting of metals. These coating materials, quite often consisting of graphite compounds, foul the nozzles and thus cause stoppage of the internal passages, leading to a variation in output at the nozzles and to a lack of regularity in the volume sprayed on the surface of the tools. Moreover, the coating material within the nozzles becomes turbulent in its flow, accelerating the fouling and consequently the blockage. In addition, the nozzles, rather inaccessible because of their number in a restricted volume, are subject to delicate adjustments, both frequent and difficult, but nevertheless necessary to assure spraying of the coating material in diverse but precise directions.
Indeed, each nozzle is independently mounted and has its own supply passages for compressed air and liquid for spraying, these three parameters multiply the chances for malfunctioning which entail unsatisfactory coating of the tools and consequent degradation of the state of their surface, thus decreasing their efficiency. In most cases, supplementary manual intervention alleviates these difficulties in spite of the inherent imperfections in the human factor.